1. Field of the Invention
The present invention relates to a wrench, and more particularly to a wrench having a wrench opening for engaging with the flat surfaces of the fasteners.
2. Description of the Prior Art
Various kinds of typical wrenches have been developed for driving hexagonal fasteners which have a plurality of substantially flat and planar surfaces that join each other at respective edges or corners of the fasteners.
For example, U.S. Pat. No. 3,903,764 assigned to Andersen, U.S. Pat. No. 4,765,211 assigned to Colvin, U.S. Pat. No. 5,219,392 assigned to Ruzicka et al., U.S. Pat. No. 5,388,486 assigned to Ruzicka et al, and U.S. Pat. No. 5,476,024 assigned to Hsieh, disclose several of the typical wrenches and comprise a substantially hexagonal wrench opening formed therein, and having rounded spaces formed in the corners for receiving the corners of the fasteners, and for allowing the fasteners to be slightly rotated relative to the wrench.
The typical wrenches comprise a number of edges or teeth or cambered bulges for engaging with the corners of the fasteners, and for driving or rotating the fasteners. However, when the edges or the corners of the fasteners are rounded or have been worn out, the fasteners may no longer be rotated or driven by the typical wrenches.
Some of the typical wrenches have rounded or curved cambered bulges extended into the wrench opening for engaging with the planer surfaces of the fasteners. However, when the wrench is rotated relative to the fastener, the edges or the corners of the fasteners will also be rotated to engage with the wrench so as to be driven by the wrench, such that the fastener can be driven by the wrench. The wrench may also no be used for rotating or driven the fasteners having rounded corners or worn out corners.
The present invention has aimed to mitigate and/or obviate the afore-described disadvantages of the conventional wrenches.